The present invention relates generally to filtering apparatus in which air or other fluids having foreign matter such as dust entrained therein is caused to flow through a filter media to deposit such foreign matter on one surface of the filter media, and a cleaning system is provided for automatically removing the foreign matter collected on the filter media surface.
A typical filtering apparatus of the foregoing type is a rotary drum filter which includes a rotating support structure on which the filter media is supported so that it assumes a generally cylindrical shape. A flow of dirty fluid, such as air, passes through the filter media from the outside surface thereof to the inside of the drum, with the dirt, dust or other foreign matter being deposited on the exterior surface of the filter media and with the cleaned air being withdrawn from the interior of the drum. It will be apparent that during use, the filtered foreign matter will build up on the exterior surface of the filter media, and it must be periodically removed to prevent the filter media from blinding.
One known arrangement for cleaning the exterior surface of the rotary drum filter includes a row of adjacent fixed suction nozzles that extend axially along the exterior surface of the drum closely adjacent to the exterior surface thereof, so that as the drum is rotated past the fixed cleaning nozzles, the suction that is constantly imposed on the suction nozzles will remove foreign matter from the filter media surface. In general, however, cleaning arrangements of this type require more suction than other types of cleaning arrangements so that operating costs are relatively high, and it is usually more difficult to control properly the desired suction to be imposed through the nozzle.
Another known arrangement for cleaning rotary drum filters of the abovedescribed type includes a structure for mechanically moving a plurality of suction nozzles back and forth in an axial direction across the exterior surface of the rotating drum filter. This arrangement usually includes a fixed track extending axially along the exterior surface of the rotary drum filter, one or more carriage members having wheels which engage the fixed track, and a chain drive for causing reciprocal movement of the carriage member along the track. The carriage members have suction nozzles mounted therein for removing foreign matter from the drum filter during such reciprocating movement, and the nozzles each have relatively long and flexible suction conduits attached thereto that will accommodate the range of movement of the carriage members from one end of the track to the other. This type of cleaning arrangement has certain drawbacks, including a relatively high cost, and a relatively large number of moving parts which are usually operating in an environment of high dust content that can adversely affect the reliability and proper operation of these moving parts. Additionally, the effectiveness of the cleaning operation itself is reduced because of the back-and-fourth or reciprocating movement of the nozzles which results in the nozzles being moved over portions of the filter element which have just been cleaned when the carriage members change direction at the ends of the track, whereby the dirtiest part of the filter element at the other end of the filter is not cleaned until the carriage has traversed the entire length of the track.
In another typically known filtering apparatus, a plurality of large, generally flat filter elements are arranged in an upright position to present generally vertically disposed filtering surfaces, the filter elements being disposed in spaced relation with the filtering surfaces of adjacent filter elements facing one another so that large volumes of air can be drawn between the filter elements and through the facing filtering surfaces thereof by any convenient suction source, such as a suction blower connected to the interiors of the filter elements, whereby foreign matter in the air is separated from the air and collected on the exposed, facing filtering surfaces of the filter elements. To conserve space, these filter elements are usually located with only a small spacing therebetween, and because of this close proximity, and the size of the filter elements, it has not been heretofore possible to provide a commercially acceptable automatic cleaning system for the filter elements, and cleaning is therefore generally done manually, using a broomlike device to periodically wipe the collected foreign matter from the filtering surfaces of the filter elements. This manual cleaning is both time consuming and expensive from the standpoint of the labor required, and can result in the filter elements not being cleaned at proper intervals because the required labor is not available.
In accordance with the present invention, a filter cleaning arrangement is provided which overcomes the above-described drawbacks of conventional filter cleaning devices, and which offers a number of additional advantages not available in such conventional devices.